Clubfoot from past to the present: A bibliometric analysis with global productivity and research trends

Clubfoot, a common congenital abnormality, affects the lower extremities; however, the literature search revealed no bibliometric research on this subject. Thus, we aimed to holistically analyze scientific articles and reveal global productivity and trend issues. This study statistically analyzed 1417 published articles on clubfoot (1980–2021) from the Web of Science database. Bibliometric network visualization maps were created to reveal trend topics, citation analysis, and cross-country collaborations. The analysis was conducted using Spearman correlation analysis. An exponential smoothing estimator was used to predict article productivity. The United States of America (433, 30.5%), the United Kingdom (166, 11.7%), and India (107, 7.5%) are the top 3 countries contributing to the literature. The Journal of Pediatric Orthopedics (220 articles), the Journal of Pediatric Orthopedics-Part B (147 articles), and Clinical Orthopedics and Related Research (69 articles) are the top 3 most productive journals. Dobbs MB (34 articles) is the most active author, and Shriners Hospital Children (44 articles) is the most active institution. Bibliometric analysis revealed that recently studied trend topics included Pirani score, Dimeglio score, Ponseti method, Ponseti casting, tenotomy, recurrence, neglected, tendon transfer, bracing, gait, risk factors, pedobarography, complex clubfoot, and polymorphism. The most studied subjects included Ponseti technique, treatment/casting, recurrent/relapsed clubfoot, Pirani score, pediatrics/children, foot deformities, surgery, ultrasound, Achilles tendon/tenotomy, gait analysis, casting, outcomes, neglected clubfoot, and tenotomy. Research leadership was determined in the western and European countries and Canada in studies and scientific collaborations on clubfoot; its impact was remarkable in India, China, and Turkey.


Introduction
Clubfoot, also known as talipes equinovarus, is a structural deformity of the foot and ankle with the hindfoot equinus (plantar flexion), varus of the heel (internal rotation), supination, and adduction of the forefoot (plantar cavus) developing early in pregnancy. [1,2] The deformity is classified into 3 different types: idiopathic (unknown cause), neurogenic (caused by nervous system status), and syndromic (related to an underlying syndrome). [3] The severity of the deformity can range from mild to manipulation-resistant extremely rigid foot.
The exact genetic mechanism of clubfoot has not yet been determined, but the underlying pathogenesis remains a matter of scientific debate. However, a multifactorial etiological model, including both environmental and genetic factors, is likely. [2,4] The incidence of clubfoot, which is one of the common birth defects, varies by geographic region. A systematic review of data published over the past 55 years shows a birth prevalence of clubfoot ranging from 0.5 to 2.0 cases/1000 live births (China: 0.51, Africa: 1.11, India: 1.19, Southeast Asia: 1.21, America: 1.74, and Turkey: 2.03 per 1000 live births). [2] Bibliometrics is the analysis of scientific outputs using various statistical approaches. [5,6] Bibliometric analysis is a method that has become popular in recent years for researching and analyzing large volumes of scientific data. Bibliometric analyzes summarize the intellectual structure of a field by analyzing the structural relationships between different research components (e.g., authors, countries, institutions, topics). Therefore, well-done bibliometric studies provide scientists with a single point of view. [7,8] It allows us to discover emerging trends and influential articles in a particular research topic or research area while providing insights into how that area or topic could move forward. Researchers can also provide new ideas for their new studies by examining past and current research trends revealed as analysis results of many articles. [5][6][7][8]

Medicine
In parallel with the need to analyze the increasing number of articles in the literature, bibliometric research was conducted on many different subjects in the field of medicine. [5][6][7][8] Clubfoot is one of the most common congenital abnormalities affecting the lower extremity, but the literature revealed no related bibliometric research. Thus, this study aimed to holistically analyze scientific articles published on clubfoot from 1980 to 2021 using statistical methods and bibliometric approaches, including citation analysis, and reveal global productivity and trend issues.

Research strategy
Web of Science Core Collection (WoS by Clarivate Analytics) database was used for the literature review. The search process was determined as 1980 to 2021. All studies with the words talipes equinovarus, clubfoot, club foot, clubfeet, club feet, clubfoot, club-feet in the title were accessed (accessed August 15, 2022 Ethical approval was waived for this study because no patients were enrolled and public databases were used.

Statistical analysis
The VOSviewer (Version 1.6.18, Leiden University's Center for Science and Technology Studies, Netherlands) package program was used for bibliometric analyzes and network maps, including citation analysis. [9] Statistical analyzes were performed with the Statistical Package for the Social Sciences version 22.0 (IBM Corporation, Chicago, IL) package program. The conformity of the data to the normal distribution was examined with the Kolmogorov-Smirnov test. The relationship between the world article productivity on clubfoot and some economic indicators of countries (gross domestic product [GDP] and GDP per capita) were analyzed with the Spearman correlation coefficient (data were obtained from the world bank). [10] The website (https:// app.datawrapper.de) was used for world map drawing. The Exponential Smoothing estimator, in which seasonal correction is considered, was used in the Microsoft Office Excel program to estimate the number of articles that can be published in the coming years according to the number of past articles. P values of < 0.05 was accepted for a statistically significant relationship.

Results
The literature review revealed a total of 1845 publications on clubfoot in the WoS database published from 1980 to 2021. The distribution of these publications are articles (1417, 76.8%), meeting abstracts (132, 7.1%), review articles (99, 5.4%), letters (80, 4.3%), proceedings papers (46, 2.4%), and the rest are in other publication types, including editorial materials, note, book chapters, book review, discussion, news item, biographical-item). Bibliometric analyzes were conducted with 1417 articles out of a total of 1845 publications in the article publication category. Of these articles, 94% (n = 1333) are in English and the rest are in other languages (German: 42, French: 17, Russian: 13, Spanish: 4, Turkish: 3, Czech: 2, Portuguese: 2, Hungarian: 1). Almost all of the articles were scanned in the science citation index-expanded (n = 1239, 87.4%) and emerging sources citation index (166, 11.7%) and the remaining few studies were social sciences citation index, conference proceedings citation index, and book citation index. It was indexed in Index-Science.

Distribution of publications on clubfoot from past to present
The distribution of the number of articles published on clubfoot by year is shown in Figure 1. The estimation values obtained by performing seasonal adjustment with the Exponential Smoothing estimation model, which is used to estimate the number of articles that can be published in 2022 and the next 5 years, are shown in Figure 1. According to the results of the model created, 82 (95% confidence interval: 64-100) estimated articles will be published in 2022 and 88 (95% confidence interval: 63-114) in 2026 ( Fig. 1).

Correlation analysis
A high level of statistically significant correlation was found between the number of articles produced by the countries on clubfoot and the GDP and GDP per capita values of the countries (R = 0.765, P < .001; R = 0.704, P < .001, respectively).

Active magazines on clubfoot
In 313 different journals, 1417 articles on clubfoot were published. Among these journals, the most active 42 journals that have published >5 articles on clubfoot are shown in Table 1, as well as the total number of citations received by the journals and the average number of citations per article. Table 2 shows the first 25 articles with the highest number of citations according to the total number of citations among the 1417 articles published on clubfoot. The average number of citations per year is given in the last column of Table 2.  [11][12][13][14][15][16][17][18][19][20]

Trending topics on clubfoot
All of the 1417 articles published on clubfoot used 1731 different keywords. Among these keywords, 81 different keywords used in >5 different articles are shown in Table 3. The cluster network visualization map showing the results of clustering analysis performed between these keywords is presented in Figure 4. A trend network visualization map made to reveal trend topics is presented in Figure 5 and a citation network visualization map made to identify the most cited topics is presented in Figure 6.

Discussion
We identified the research leadership of Western countries, especially the USA, European countries, and Canada in research and scientific collaborations on clubfoot, but its impact was remarkable in developing countries, such as India, China, and Turkey. The article productivity of the world countries revealed that 13 of the most productive countries that contribute the most to the literature on clubfoot are developed countries, including the USA, United Kingdom, France, Germany, Canada, Italy, Israel, Sweden, Austria, Australia, Japan, Netherlands, and Switzerland, and Pakistan, India, China, Turkey, and Brazil, except Egypt, were developing countries. Among the developing countries, India, China, Turkey, and Brazil were countries with large economies. The high level of significant correlation between the number of articles published by countries on clubfoot and GDP and GDP per capita values suggests that the economic development level of countries is primarily effective in the productivity of global articles on clubfoot. Many bibliometric studies in the literature emphasized the positive effect of the development level of countries on academic productivity. [5,7,8] The density map created according to the cooperation density between the countries determined that the countries with the highest cooperation were the USA, England in the United Kingdom, Scotland in the United Kingdom, Australia, Switzerland, Canada, Netherlands, Ireland, France, New Zealand, and Germany. The international co-authorship cooperation of the countries on clubfoot mentioned the effect of the geographical neighborhood in the studies (countries located in the same cluster and are geographically close include Iran and Saudi Arabia; Australia and New Zealand; England and . This study recommends that researchers who want their work to see more impact after publication should first consider these journals. The sorted articles according to the total number of received citations determined that the most cited study was the article titled "Long-term results of treatment of congenital club foot," by Laaveg and Ponseti (1980) published in the Journal of Bone and Joint Surgery-American Volume (11th), followed by "Radical reduction in the rate of extensive corrective surgery for clubfoot using the Ponseti method," by Morcuende et al (2004) [16] published in Pediatrics, "Treatment of idiopathic clubfoot -a 30 year follow-up note" by Cooper and Dietz (1995) published in the Journal of Bone and Joint Surgery-American Volume, [11] "Classification of clubfoot" by Dimeglio et al (1995) [13] published in the Journal of Pediatric Orthopedics-Part B, and "Factors predictive of outcome after use of the Ponseti method for the treatment of idiopathic clubfeet" by Dobbs et al (2004), [12] in order.
The evaluated articles according to the average number of received citations per year revealed that the most effective study is by Morcuende et al (2004), [16] followed by Dobbs et al (2004), [12] Cooper and Dietz (1995), [11] Dimeglio et al (1995), [13] and Herzenberg et al (2002) [14] entitled "Ponseti versus traditional methods of casting for idiopathic clubfoot" published in the Journal of Pediatric Orthopedics, in order.
Our literature review could not find a comprehensive bibliometric study on clubfoot. Only Malik and Noordin (2019) identified the top 100 most cited studies on clubfoot. [21] Our study focused on all aspects of clubfoot. This study is the first bibliometric research on clubfoot; thus, it is expressed as an important advantage. The presence of bibliometric analyzes on international collaborations, global productivity, and Table 1 The 42 most productive journals that have published more than 5 articles on clubfoot. trend research can be expressed as other advantages of our study in addition to our citation and co-citation analyzes. Our study limitation is the limited database, which only includes the WoS database. However, bibliometric analysis is not preferred because citation analyzes cannot be performed in the Pubmed database. Some journals with low impact levels are also indexed in the Scopus database. [22,23] The most important reason why we prefer the WoS database is that it indexes the articles published in journals with a higher impact level (journals scanned in science citation index-expanded and emerging sources citation index indexes) compared to other databases. Additionally, WoS was widely preferred in other bibliometric studies in the literature. [5][6][7][8]

Conclusion
Scientific production on clubfoot has chronologically increased over the years. There are significant international collaborations globally, but clubfoot research is thought to be encouraged, especially in underdeveloped countries. These results may provide new ideas for future research.